從組合框類中按索引獲取值

我正在從 vb6 接近 vbnet，我正在嘗試使用包含我存盤的值的類從組合框獲取值。這里是類

        Private m_ItemText As String
        Private m_ItemIndex As Int32

        Public Sub New(ByVal strItemText As String, ByVal intItemIndex As Int32)
            m_ItemText = strItemText
            m_ItemIndex = intItemIndex
        End Sub

        Public ReadOnly Property ItemIndex() As Int32
            Get
                Return m_ItemIndex
            End Get
        End Property

    Public ReadOnly Property ItemText() As String
        Get
            Return m_ItemText
        End Get
    End Property

我用這個方法給combobox充電

        ComboBox2.Items.Add(New clsComboBoxItem("sometext", 1))
        ComboBox2.Items.Add(New clsComboBoxItem("sometext 2", 2))
        ComboBox2.Items.Add(New clsComboBoxItem("sometext", 3))

這在combobox.selectedindexchanged

        If ComboBox2.SelectedItem.GetType.ToString = itmCombo.GetType.ToString Then
            itmCombo = CType(ComboBox2.SelectedItem, clsComboBoxItem)
            MessageBox.Show("Item Text=" & itmCombo.ItemText & " and ItemIndex=" & CStr(itmCombo.ItemIndex))

        End If

誰能告訴我如何通過存盤在類中的索引獲取元素？例如，將“2”寫入文本框，組合框應顯示“sometext2”。假設我想擴展類添加一些值，如 m_ItemText2、m_ItemText3 等，我將學習一種獲取所有這些值的方法。我希望我很清楚 提前謝謝

uj5u.com熱心網友回復：

如果你有一個DataSource組到DataTable你ComboBox，剛才設定的DisplayMember和ValueMember。我的測驗 ComboBox 設定為DropDownList.

Private Sub FillComboBox()
    Dim dt As New DataTable
    Using con As New SqlConnection(ConStr),
        cmd As New SqlCommand("Select FlavorID,FlavorName From Flavors", con)
        con.Open()
        Using reader = cmd.ExecuteReader
            dt.Load(reader)
        End Using
    End Using

    ComboBox1.DisplayMember = "FlavorName"
    ComboBox1.ValueMember = "FlavorID"
    ComboBox1.DataSource = dt
End Sub

顯示值 要顯示轉換為 DataRowView（即 中的物件Item）的 Text ，請提供所需的欄位并呼叫 ToString。

Private Sub ComboBox1_SelectionChangeCommitted(sender As Object, e As EventArgs) Handles ComboBox1.SelectionChangeCommitted
    MessageBox.Show(ComboBox1.SelectedValue.ToString)
    MessageBox.Show(DirectCast(ComboBox1.SelectedItem, DataRowView)("FlavorName").ToString)
End Sub

如果是一項一項的添加，仍然可以設定DisplayMember和ValueMember。

'https://stackoverflow.com/questions/38206678/set-displaymember-and-valuemember-on-combobox-without-datasource
 Private Sub SomeFormsLoadEvent()
    ComboBox1.Items.Add(New KeyValuePair(Of String, Integer)("Ultra-fast", 600))
    ComboBox1.Items.Add(New KeyValuePair(Of String, Integer)("Fast", 300))
    ComboBox1.Items.Add(New KeyValuePair(Of String, Integer)("Medium", 150))
    ComboBox1.Items.Add(New KeyValuePair(Of String, Integer)("Slow", 75))

    ComboBox1.DisplayMember = "Key"
    ComboBox1.ValueMember = "Value"
    ComboBox1.DataSource = ComboBox1.Items
End Sub

我發現顯示文本有點復雜。我必須將專案轉換為其基礎型別 (KeyValuePair)，然后詢問 Key 值。

Private Sub ComboBox1_SelectionChangeCommitted(sender As Object, e As EventArgs) Handles ComboBox1.SelectionChangeCommitted
    MessageBox.Show(ComboBox1.SelectedValue.ToString)
    MessageBox.Show(DirectCast(ComboBox1.SelectedItem, KeyValuePair(Of String, Integer)).Key)
End Sub

uj5u.com熱心網友回復：

據我了解，您希望將值存盤在一個類中并通過組合框顯示和訪問它們。這種方法怎么樣：

值的類：

Public Class clsValues

Private lstItemTexts As New List(Of String)


Public ReadOnly Property AllValues As List(Of String)
    Get
        Return lstItemTexts
    End Get
End Property

'To initialize class with empty list, items can be added with AddItems
Public Sub New()

End Sub

'To initialize class with items, items can still be added with AddItems
Public Sub New(lstItemTexts As List(Of String))
    Me.lstItemTexts = lstItemTexts
End Sub

Public Sub AddItem(item As String)
    Me.lstItemTexts.Add(item)
End Sub

Public Function GetItemByIndex(index As Integer) As String
    Return lstItemTexts(index)
End Function

Public Function GetIndexByItem(item As String) As Integer
    Return lstItemTexts.IndexOf(item)
End Function

End Class

您可以宣告它并像這樣填充值：

 Private Values As New clsValues()
 Values.AddItem("Some Text 1")
 Values.AddItem("Some Text 2")

或者

Private Values As New clsValues(New List(Of String)({"Some Text 1", "Some Text 2"}))

從組合框獲取值

Private Sub ComboBox2_SelectedIndexChanged(sender As Object, e As EventArgs) Handles ComboBox2.SelectedIndexChanged

    MessageBox.Show(Values.GetItemByIndex(ComboBox2.SelectedIndex))

End Sub

uj5u.com熱心網友回復：

@Mary 所說的是真的 ComboBox 具有有用的值 請參閱下面的代碼 將 gvTxType 更改為 TextBox 以在單擊 tvTxType 時查看結果

    Private Sub cbTxType_SelectedIndexChanged(sender As Object, e As EventArgs) Handles cbTxType.SelectedIndexChanged
    If cbTxType.SelectedIndex > -1 Then
        'Dim sindex As Integer
        'sindex = cbTxType.SelectedIndex
        'Dim sitem As String
        sitem = CType(cbTxType.SelectedItem, String)
        'MsgBox("You Selected " & sitem)
        'Index is ZERO based
        gvTxType = sitem
    End If
End Sub

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